Telephone system



TELEPHONE SYSTEM Filed 001:. 22, 1940 3 Sheets-Sheet 1 FIG-l INVENTOR A. H. INGL IS A 7' TORNE V Oct. 19, 1943. A. H. INGLIS 2,332,448

I TELEPHONE SYSTEM Filed Oct. 22, 1940 3 Sheets-Sheet 2 lNVEN TOR By A. H. lNGL IS W WW? A T TURNE V Oct. 19, 1943. [NGLlS 2,332,448

TELERHONE SYSTEM Filed Oct. 22, 1940 3 Sheets-Sheet 3 76 53 WM ELEMENT HAW/v6 64 a fir- V 5.55%??? 65 79 73 c ARACTER/JT/CS 66 lo 7 FIG. 4

' 60 6/ CURRENT SOURCE l 62 $1 CENTRAL OFF/CE F/G. 6 Q \0 4a 92 lg Q A $3 VOLTAGE APPLIED 7'0 R/NGER F 6. 8 s 70 7/ FIG. 7

E TIM 46 TIME INVENTOR By A. H. lNGL/S 7m 6 f ATTORNFV Patented Oct. 19, 1943 onireo STATES TENT. OFFICE 8 Claims. (01. 177-7) This invention relates to'telephone systems and particularly to improvements in subscribers telephone equipments. Y

The objects of the invention are, to improve the ringing equipment in subscribers telephone sets, to provide greater fiexibilityin the sound output of the ringer when the subscriber is called, and to effect other improvements in telephone systems.

Heretofore arrangements have been proposed in which when a subscriberjis called, ringing signals were gradually increased in sound intensity until the subscriber answersby means of equipment whereby the ringergongs are normally mechanically damped so. that, when first actuated they emit a subdued sound and whereby as the ringing current continues a bimetallic heater element functions to mechanically and gradually lessen the damping of theringer gong so as to gradually increase the sound output thereof.

It is a featureof the applicants invention to avoid mechanical damping meansfor ringers in subscribers telephone equipments to gradually increase the sound intensity by providing a ringer operative to increaseits sound intensity in response to an increase in the applied ringing current and by providing a separate means associated with said ringer for gradually increasing the operating voltage across the ringer from an alternating current source of constant voltage at a central ofiice, This increase in voltage causes the increased flow ofcurrent, through the ringer.

It is another feature otthe applicantsinvention to provide such separate means consisting of a resistance element having negative resistance-current characteristics, suchas a boron or so-called thermistor element for example, which increases in temperature as a "constant voltage is applied across itto produce a gradual in-' crease in voltage across and-current through the element. Thus a ringer in'series withthis ele ment which operates with "a sound intensity that increases with increase in current will becontrolled to increase the sound intensity accor ingly.

sound intensity to the full volume within a comparatively short period of time, while'still other subscribers mayhdesiredifierenttiming periods during which the ringer will attain its full volume at different periods of day or night to meet specific requirements. To this end elements having correspondingly different non-linear resistance characteristics are provided in the form of individual capsules or other suitable units-and These capsules maybe inserted between clamps connected in circuits with the ringer.

It is another feature of the applicants invention to provide, in conjunction with the arrangement for gradually increasing the sound intensity of. the ringer, arrangements whereby the sound intensity may be changed and held at any one of several constant values,for example, the subscriber may desire a constant low sound 01' thesringers or an intermediatesound or a sound of high intensity at different periodsof the day or night. v v I It is another featureoi the'applicants invention to provide in a telephone set manually op- .erated mechanism such as switches, for adjusting and Controlling the insertions and removals in the circuits, for the ringer oi the. resistance elements having. negative resistance characteristics'or the pure resistance elements to produce the desired soundintensitiesrequired..

A ringer unit suitable for use iii-connection I with arrangements of this Kind may be oi'tne type disclosed in the copending application or Dickt'en and H. C. Harrison, Serial No. 362,204,

current applied andthe sound intensitymay be regulated from a soft pleasing sound to a more arresting sound of greatervolume while the time during which the increasing 1 sound intensity takes place may be variedby the characteristics of the" elements thatmay be inserted and interchanged in the'telephone set orthe sound 'intensity may be changed to different constant volumes as required.

This invention has been illustrated in the accompanying drawings in which:

Figs. 1, 2 and 3 show various views of a subscribers telephone set arranged in accordance with applicants invention.

Fig. 1 is an interior view of the housing and the bottom plate showing the location of the various instruments located therein;

Fig. 2 is a side view of the set with a portion broken away to show the control switches and resistance elements;

Fig. 3 is a rear view of the set showing the exterior portions of the switches;

Fig. 4 is a diagram showing "a telephone circuit in which the applicants invention has been incorporated;

Fig. 5 shows a modified circuit of a portion of the applicants invention as applied to a telephone circuit;

Figs. 6,'7 and 8 show various curves relating to the functioningof the 'app'licants invention; and

Fig. 9 shows a type of thermistor element and its mounting.

Referring :now to the drawings, the telephone set consists of the housing I having a cradle portion 2 in which the usual handset, not shown,

may be placed to control switching contacts -3 through the medium or 'a cradle member 4 acted upon by a plunger 5 so thatwhen-the handset is resting in the cradle, switching contacts 3 are opened to disconnect the telephone set from the central ofiice line and when the handset is re-- moved the contacts 3 are closed to connect the telephone circuit to the line. At the front of the housing is mounted the usual dial mechanism 8. Inside the housing at the rear thereof are mounted theswitche'sil; '10 and H having control levers I2; 'l3'and ll; respectively eirtendingputside of the housing. These switches are of the type in which the levers 1-2 and M maybe moved in three different positions to close sepa rate connections andthe-switch lll is 'of the type in whichthe lever l3 r'rlly'be 'rhovedi-none direc tion to close a single connection. Thehousirig i rests on thebott'om plate l8 which i are mounted-on the'inside thereof condenserl? "and'on a mounting plate I8 as showntw'o thermistorelements and four resistance elements 22. On the bottom plate is also mounted a ringer 2301 the type suitable forus'e in connection with'the present disclosure. In place of the arrangements of these thermistors 20 as shown inFig. 1, the are rangement maybe arranged inaccordancewith that shown in Fig. 9 namely a. thermistor element may be enclosed in a vessel or capsule 26 having metal caps Z'land -28 to which the terminals of the thermistor. element areconnected. This capsule maybe inserted betweenthe clips 29 and .30 which may be mounted on the mounting plate l8. It is evident thatmqrethan one of these capsules may be employed if required and that capsules having thermistor elements of diffe'rent characteristics maybe inserted and replaced by other elrnents toprovi de io'r ambient requirements. With register to the ringer 2's, it may be of sllh fi nstlll c tid'fi astb- "change its sound inte I'iSity'with changes cws'rentpassing through it. The ringer may co'nsist of there's-oior -armature "con'slsting of a'p'ern'ra'nent magnet of softiron poles which'ifs rotatahlewithihthe pole pieces 36 and 31 of thestator consisting of a laminated structure on which "the energizing "the sound intensity depends on the current apd to the coil various effects may be produced by changes in the current supplied. This change in sound intensity is illustrated by curve 43 in -Fjig. 6 which represents the increase in sound intensity as measured by decibels for variousvoltages applied to the ringer. The thermistor characteristics may be illustrated by the curve 48 as shown in Fig. 7. This curve indicates how the resistance decreases with the passage of time and the consequent increase in current through the elements.

A description will not be made of the functioning of the applicants invention in connection with the circuit diagram shown in Fig. 4. The telephone circuit consists of the usual handset 50, switching contacts 5|, induction coil 52, dial 53 and a ringer 54 of the type suitable for use in this arrangement in series with a condenser '55 and the tip and ring conductors T56 and R51 to a central oflice which is indicated diagrammatically in sufi'icient detail to illustrate the application of ringing current from an alternating or direct current source 59 by the operation of a key 60 or -by the application of ringing current from source 59 at intervals by the operation of key Bl which connects the source at intervals through "an interrupter 62. Tnecontrm of the operation of the ringer '54 to regulate its sound intensity is efiected by the switches 8, 1 fl-a-nd i l, resistances 63, 64; 65 and 66 and thermistor elemerit-61in various manners as will be hereinafter described.

If-rei'erence-is first made to Fig. '8, the curve 70 indicates the increase in sound intensity as measured by decibels with the passage of time, when a steady-alternating current is applied by the operation of key 6'0 from the source 59. If lrey'B-I is operated and the current from source 59 is interrupted 'by the interrupter 62 the operatio'n-of the'ringer'54 will be intermittent and due to these intervals between the application of ringing current, the'volum'e as measured in decibels'of the ringer will increase in intensity at 'a r'riuchslower rate as for example is indicated by the'curve H. such and various-other controls over the operation of ringers may be exercised by the manipulation of keys "8, l0 and II andrnaybe outlined as follows: It may be desired, rtrexampi -to have the sound intensity "of a constant volume but comparatively low in tone, 'or'of a medium or higher to'ne'd steady 'sound intensityma'y be required. on theother hand it may be required to have the sound'st'art immediately upon the operation of the control switches and the application of the ringing current with a low soun'dintensity that increases in volume with the passage of-time or itmayhe required that the starting be delayed "for some "short period after the ringing current has been applied. This latter't-y'pe of control may'be required {in case, ror example; for secretarial extensionsor-similar arrangements "where a "call is to be answered by a secretary m in the event that the party at the main station does not answer the call immediately. With these various types of controls in mind, detailed descriptions willnow be made. If a low constant sound intensity is required, the switch 9 may be operated to establish a connection at contact .13 and switch H may be operated to establisha connection at contact 14. Thus a circuit for the ringer is extended from the ring conductor REF, condenser 55, ringer 54, resistance 64,.contact '13 of switch 9, contact M of. switch H,,back tothe tip conductor T56. sistance E54 is comparatively high and in series with the ringer and consequently the ringer will operate with a low intensity at a constant volume when ringing current from source, 59 is applied at thecentral oilice by the operation of key (ill. If a medium constant volume is desired, theswitch 9 is operated to establish a connectionfat contact l and switch II is operated to establish a connection :atcontact 14. In this case the circuit for the ringer 54 extends through the resistance 63, contact'15 of switch 9, contact 14 of switch H. As the resistance '63 is some-* what lower than 64, the ringer will operate with a constant volume of medium intensity. If a high constant volume is required, the switch 9 will be operated toestablish a connection at contact it and the switch H will remain toestablish aconnection at the contact 15. In this case the circuit for the ringer '54 extends-through the ringer directly through contactfllfi at Switch 9 and contact 74 at switch ll without any resistance in series and will consequently produce a sound of higher intensity. In case a sound intensity increasing with time and starting im- Inthis case the remediately is required, the switch H is operated to establish a connection at contact i8 and the switch iii is operated to close a connection at contact E8. A circuit for the ringer now extends through the thermistor element 61, contact 18 of the switch ii to the line and another connection is established in parallel of the thermistor 61 through resistance 65 and contact 19 of switch Ill. Thus the thermistor 61 is shunted by resistance 65 which is of a rather high resistance so as to produce a sound intensity that increases with time, for example in accordance with the curve H3 of Fig. 8 and the operation of the ringers starts immediately upon the application of the ringing current from source 55 If it is desired that the volume should increase with time but with a delay in starting for a short period after the application of the current from source 59, switch II is operated to establish a connection at contact 89. In this case the circuit for the ringer is extended through thermistor element 6?, resistance 65 and contact 88 of switch H. As the resistance this comparatively low but in series with the thermistor, Bl, there will be a short delay in starting the operation of the ringer after the current has been applied at source 5% Intermittent ringing, current is applied from the central cities by the operation of key 6! and if the thermistor element 6? is inserted in series with the ringer directly through resistance 66 or over the resistance 65 in shunt of the thermistor element 6? the ring-.

er will operate intermittently and the volume will increase with time at a lower rate than when a steady ring is applied, somewhat along the lines as indicated by the curve H. It is evident that theseresistance values mentioned may be varied and that the switches 9, l0 and H maybe manipulated differently at different periods of thefnight or day as desired by the subscriber to secure corresponding sound effects from the ringer.

A modified arrangement of thermistor elements maybe made in accordance with the applicants invention as illustrated in Fig. 5. nFor example, a pair of thermistorelements ti] and SI and switches 92 and Q3 may be provided in place of the thermistor'element 67 in-the circuit shown in Fig. 4. In this case the switch 92 may be operated to include-either of the thermistor elements 96 oriii 01' the switch 93 may be operated to include both thermistor elementsflfi and 8| in parallel in the circuit shown in Fig. 4. Thus the operating characteristics of the ringer may be 'changedin accordance with the negative characteristics of these thermistor elements as connected in the different combinations by the switch 92 or 93. The thermistor element 6'! may also readily bechanged by having an arrangement as shown in Fig. 9 whereby capsules such as shown in this figure may be interchangedand in which the thermistor elements have difierent characteristics; Such interchanges may, of

course, take place without disturbing any of the 2. The combination of a ringer having char-' acteristics suchthat its sound intensity increases proportionally to the increase in operating current applied thereto, with a source of alternating current, a plurality of elements each having a difierent negative resistance switching means for connecting any one of said elements with said ringer and said source of current inv series, each of said elements responsive to current from said source for applying to said ringer current that will increase from a minimum to a maximum within its different corresponding time period to cause the ringer to increase its sound intensity accordingly.

3. The combination of a ringer having characteristics such that its sound intensity increases proportionally to the increase in operating current applied thereto, with a source of current, an element having a negative. resistance char acteristic, whereby resistance decreases at certain rates with time as a certain voltageis applied across it, a resistance connectable across said element to decrease the normal rate of change thereof, a circuit and switching means for connecting said element in parallel with said resistance and in series with said ringer, and means for applying current from said source to said circuit to cause said ringer to respond to increase its sound intensity at the rate determined bysaid element and said resistance connected across it.

4. The combination of a ringer responsive to increase. in current to operate with a sound intensity that increases at a rate corresponding to the rate of increase of current in said ringer, with a source of current, a resistance element having negative resistance characteristics, a resistance characteristic,

connectable in series with said element, and means for connecting said ringer in series 'with said element, resistance and seurce of current to cause said ringer to be actuated a certain interval after the source of current has-been applied at a rate increasing with time as determined by the negative characteristics of said element.

5. The combination of a line with a ringer at one end thereof operative to increase its-sound volume output in response to a corresponding increase in current passing through it, a source of current 'of constant voltage connectable to the other end of said line and means having a negative resistance characteristic connected to the line at the same end asrthe ringer and in series therewith responsive to current from said sourcewhen said source is connected to the'opposite end of said line for gradually increasing current through said ringer to cause it to change its sound volume output accordingly.

6. The combination of a line with a ringer at one end thereof operative to increase its sound volume output in response to a corresponding increase in current passing through it, as'ource of current of constant voltage connectable to the other end of said line, and means having a negative resistance characteristic connected to the line at the same end as the ringer and in series therewith responsive to current from said scurce'when said source is connected to the opposite end of the line for applying to said ringer current from said source that will increase from a minimum to a maximum value within a definite time period to cause said ringer to increase its sound volume intensity accordingly within said definite time period.

7. The combination of a line with a ringer at one end thereof having characteristics such that its sound volume output increases proportionally to the increase in operating current applied thereto, a source of current of constant voltage conn'ectable to the other end of said line, a plurality of difif'e'rent resistance units at the same end of the line 'as' the ringer, a circuit and switching means at the same end of the line as the ringer for connecting any resistance unit in series with the ringer in the line, and an element having negative resistance characteristics connectable by said circuit and switching means to the same end of the line as the ringer and in series with a connected resistance unit and the ringer, and responsive tothe current from said source when said source is connected to the opposite end of the line for gradually increasing current through the ringer as controlled by said element and modified by the connected resistance unit to cause said ringer to change its sound volume output accordingly.

8. The combination of a line with a ringer at one end thereof operative to increase its sound volume output in response to a corresponding increase in current passing through it, a source of current of constant voltage connectable to the other end of said line, and means having negative resistance characteristics connectable to the line at the same end as the ringer and in series therewith responsive to impulses of current from said source received over said line for gradually increasing the current of said impulses through said ringer causing a change in sound volume output for each succeeding impulse of current. ALFRED H. INGLIS. 

